1. Field of the Invention
This invention relates generally to surgical devices and more specifically to electrosurgical catheters adapted to incise body material defining a body conduit.
2. Discussion of the Prior Art
Various surgical devices have been used to electrosurgically ablate or otherwise cut body materials. In this type of surgery, electrosurgical energy is passed between two electrodes creating a high current density which ablates the body materials. In a typical monopolar system, the patient is coupled to a large grounding pad which forms one of the electrodes. The electrosurgical device forms the other electrode. In this system, the electrosurgical device provides a very low surface area and consequently a very high current density for ablation or cutting in proximity to the device. In a bipolar system, the two electrodes are included in the device and high current density is achieved in the small area between the electrodes.
These electrosurgical devices include a catheter having a balloon and an electrode extending over the surface of the balloon as disclosed in applicant's co-pending applications, Ser. No. 08/241,007, filed on May 11, 1994, and entitled "Angioplasty Catheter and Method for Making Same", and Ser. No. 08/216,512, filed on Mar. 22, 1994, and entitled "Improved Catheter with Electrosurgical Cutter". The entirety of this disclosure is incorporated herein by reference. This catheter is used in a monopolar system where an electrode, in the form of a wire, is disposed over a radially expandable balloon of the catheter. As the balloon is inflated, the electrode is carried radially outwardly into proximity with the body material to be ablated or cut. Although it has always been of interest to increase the current density associated with the wire electrode, this has been difficult to achieve as smaller wire sizes necessarily result in reduced electrode strength and integrity. The balloon material has also been restricted to insure against over-expansion and electrode proximity. Materials forming non-distensible balloons have been preferred, but have made it difficult to achieve a low-profile state for insertion.